Generally, polymer film capacitors consist of two metal electrodes separated by a layer of dielectric film. The two metal electrodes can be relatively thick, on the order of 3 to 100 um, to create a film-foil capacitor. Or the metal electrodes can be deposited directly on to the polymer film, a thickness of less than 1 um, thereby creating a metalized film capacitor. Artisans practiced in the art also combine these electrode styles, creating hybrid film capacitors.
One of the issues preventing wider spread adoption of film capacitors is the limited temperature range. Most polymer film capacitors use polymer resins with glass transition temperatures less than 150° C. This limits the continuous use operating temperature to typically less than 120° C. Capacitors manufactured with higher glass transition temperature polymers include PPS (polyphenylenesulfide), PI (polyimide, e.g., Kapton), PC (polycarbonate), and PTFE. However, these and other polymers have lacked additional properties required to make film capacitors. A few of these additional desired properties are low dielectric loss, an ability to self-clear, high dielectric strength, and high mechanical strength.